Conventional ignition interlock devices disable a vehicle under certain conditions, so that its engine cannot be started. Such a mechanism can be used to reduce drunk driving, by requiring a prospective driver to submit to a blood alcohol level test prior to starting the engine. The prospective driver can be required to exhale into the device; if the detected breath-alcohol concentration indicates a blood alcohol concentration greater than a threshold amount, the vehicle's starter can be disabled, so as to prevent the vehicle from being driven.
Many jurisdictions require ignition interlock devices to be installed in vehicles under certain circumstances; for example, prospective drivers convicted of driving under the influence of alcohol may be required to have such a device installed in their vehicles for some period of time after the conviction. Such requirements vary from jurisdiction to jurisdiction.
Existing ignition interlock devices are relatively inflexible, however, and they fail to adapt to or respond to current situations. Thus, the requirement to submit to the blood alcohol test can be unduly burdensome at certain times or in certain situations when the risk of drunk driving is relatively low and the test is relatively unnecessary. Conversely, the testing requirements may be too lax at other times when the prospective driver is at greater risk of driving under the influence, or when it is easier for a prospective driver to defeat the test.
The relative inflexibility of existing ignition interlock devices, and their relative inability to adapt to current situations and contexts, limits the effectiveness of such devices in reducing driving under the influence.